Ugh. Brakes

I taxied the plane today getting ready for first flight. The plane is great when it is rolling, but the brakes screech and (if pressed hard) shudder. I read threads which suggest beveling the pad edges, putting some lubricant and anti-squel on the structure, etc. I talked with Cleveland and they suggested a light sanding of the pads and discs to break the glaze and then recondition. I am not sure what is the best solution. Suggestions appreciated.

Same here,,,

Had cleavland breaks in the past and they squealed when new pads went on. Switched to Grove breaks a couple years ago and they didn't sqeek, but had a bit of drag when new. Just completed a Conditional Inspection today and put new pads on. The breaks got hot after taxi'n down the 8000' to the run up area, could smell them pretty good and took a bit more power to keep her moving. Not good. Have been told to "break 'em in" and "you have to seat them a bit (wear them down, I guess.).

Anyway, I'm curious also about other people's experiences?

I'm careful to keep any bit of my big feet off the breaks too! Not me dragging them. Hahaha

-rotor

Make sure the aluminum brake line is bent such that it does not preload the caliper in either direction. Caliper should wiggle easily in either direction with finger pressure. Be confident there is no air in the lines. Actually DO the Cleveland break-in procedure. It is more than just a tap at normal taxi speeds. Hit 'em HARD from high speed. (OMG yes, the dreaded high speed taxi ) Let them cool and do it again.

break-in procedure A or B?

Cleveland says to do this:

http://www.aircraftspruce.com/catalog/pdf/liningconditioningprocess.pdf

but then they say there is now only one kind of lining, no longer organic and metallic versions...

....so which process do we use? the drag'em for 1500', or 'hit em hard' version????

For a number of years Cleveland offered standard organic & heavy-duty asbestos brake linings for their wheels and brakes.

In January 1988 the two types of linings were discontinued and a single, improved brake lining was introduced. The prices are higher than the older types of linings but performance and durability are greatly improved. Replace worn brake linings with new original Cleveland parts for positive braking action. Advise make, year and model number of aircraft, and order number of linings you require plus required number of rivets.

Most light aircraft take 2 linings per wheel. See tool section for economical rivet tool. Most brake linings include rivets, few are sold as pad only.

Advise aircraft make, model and serial number to assure that correct brake lining part number is furnished. Extra rivets, P/N 105-2, for all models listed in table .05 each

Some pads have them already, if not, I filed a notch in the top edge of the pad the same depth as the rivet is from the face; I can now see at a glance how much pad is 'really' left ( assuming it wears pretty evenly, which isn't always true).

The break in procedure for brakes, is to deposit a film of material on the disc. When braking the pads generate a gas and it will also deposit some material on the rotor. This is needed for consistent friction and wear.

Think about high performance land vehicles, slotted and drilled rotors. This allows the gas film to escape. I have had trouble on my car brakes and it also recommended a break in procedure just like Cleveland. Just DON'T STOP AND HOLD BRAKES WHEN HOT. It will leave a spot on the rotor and they will shudder when applied afterwards.

Your comments brings home something Cleveland tech support mentioned yesterday. If the brakes shudder, take a 600 grit sandpaper and sand the face of the disc both sides. They are probably addressing your comment about a spot on the disc.

brake theory

Two cents from an RV builder who also sells auto brakes:

Auto rotors use a "non directional" finish when they are new or refinished. This can be accomplished with a round disc or emery cloth.

When new, it's never a good idea to have hot brakes. As stated in an earlier post, they will off-gas and glaze the pads when they get hot.

Best case is to do 10-15 stops with cooling periods in between. Obviously not the easiest task when the prop is pulling the airframe.

Bottom line is, just don't overheat when new if at all possible. Brake pad will endure much more heat once they are broken in to the rotor.

Our pads are small, and they don't have alot of material to dissipate heat as well as auto pads, so we just need to take extra care in breaking them in.

As I said, just 2 cents crossing over from the auto brake biz.

When you say "shudder" are you talking about the feel of the brakes or an actual noise?

Because if it's a noise -- a groan -- , try taking the brake pads off, remove the inboard one and spread some CRC Disc Brake Quiet where it meets the piston on it. Wait a few minutes (you can install when tacky) and reinstall. If it's a groan, that will eliminate it.

Back in the stone ages when I got my finishing kit, the brake rotors were painted. I used lacquer thinner to remove it on the surfaces of interest. I don't know if they still paint them, but if so, I'd suspect it becomes a bit of a mess until it is completely burned off. It could be causing your problem.

Mine didn't shudder, but they did squeal ans squeak for a little more than 15 hours.

I just put up with it and it disappeared on its own after everything wore in.

CJ

Your master cylinders are not releasing. Check at the pedals. They must be very loose or they will bind. It is the last 1/16 in of travel that releases pressure. Very common problem. Terry

shudder and groan

The first original attempts to brake gave a squeal. After trying to condition the brakes as Cleveland suggests - 1500 ft taxi at 10MPH with prop at 1800 rpm - the brakes would shudder on a hard stop with the vibration shaking the plane enough that the altimeter was vibrating +- 40 ft. When I do not brake, everything is quiet and the plane rolls easily.
I took the brakes apart, added the no squeal fluid to the rear of the inner brake backing plate. This reduced the clearance in the brake, but I could still shift it back and forth slightly. I then sanded the brakes with 600 grit and put a slight bevel on the pads fore and aft. Out I went with success in mind. There was improvement - no shudder, but still a definite squeal. I am thinking of letting it mature for a few flights as the brakes (and airplane) are new. Then I will go through the conditioning again. I will also look at the brake pedal release. I have stainless steel lines going from the cockpit to the brakes and I am wondering if they are too rigid??

Hi Jay,
Wonderful to hear that you are close to the maiden. Please e-mail some pictures.

No back to your problem. I have a different opinion about it and think it is a resonance. I have seen this go away by just putting a 6-12 inch length of rubber hose over the coiled part of your ss brake line. Split it to get it on and secure it with clamps.

Secondly - do you have proper stiffeners in as shown in one of my builder logs here. http://www.mykitlog.com/users/display_log.php?user=jan&project=2090&category=4871&log=163648&row=2